


In the Darkness Beyond the Ordinary

by lawrencetheshark



Category: Undertale (Video Game)
Genre: After Hours, M/M, ambiguous genitalia, bar counter sex, goopy Gaster, ill spare yall the tentacle dicks for now
Language: English
Status: Completed
Published: 2016-01-16
Updated: 2016-01-16
Packaged: 2018-05-14 06:29:13
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,698
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5732959
Author URL: https://archiveofourown.org/users/lawrencetheshark/pseuds/lawrencetheshark
Summary: <blockquote class="userstuff">
              <p>Grillby can't help himself from thinking about Gaster after hours.</p><p>Please be sure to read the beginning notes</p>
            </blockquote>





	In the Darkness Beyond the Ordinary

**Author's Note:**

> holy shit you guys this thing is over 2500 words
> 
> what have i done
> 
> hrrrg anyway a while ago i wrote a post on tumblr about some goopy gaster headcanons which you can read here http://jaspertheshark.tumblr.com/post/136298302885/ 
> 
> then my friend, tumblr user squeekz4all sent me some delectable sin (which i have included at the beginning of this fic)
> 
> and well!!! it inspired this long-winded and probably terrible onslaught of smut.
> 
> have fun anyways my fellow sinners

_The bartender elemental was a bit curious about the scientist's form, since he kept a simple fire that could vary in intensity but couldn't change shape like the goopy W.D Gaster, when drying a cup at his restaurant he quietly hummed thinking about touching the goop, even though he never could in fear of burning the other monster. Thoughts of Gaster nuzzling up against him somehow without getting hurt, covering his body in kisses and gentle teasing touches... He thought about them both holding each other, humming and sighing quietly as Grillby's body crackled softly in the background, they both hold hands as the fire monster rolls his hips, the goop slowly separates just enough to form a mostly solid form, just enough to be held and peppered in kisses as cum began to drip from the void between Gaster's legs. With a shaking breath they held each other as Grillby's began to buck his hips faster, panting against the cracks of Gaster's face. Shifting the other's glasses back into place W.D's hands wandered about, admiring how the fire shot through the holes of his hands. If he wasn't making sensual comforting, he'd take notes on Grillby's body, how some parts of him seemed hotter, the flames varying from a dull yellow or deep red to borderline cyan by his crotch. As time passed, the two began to shake, crying out into the empty room enjoying the slam of orgasm as they both splattered their colors all over the sheets_

 

After hours Grillby found himself curious about Gaster’s body. It was recently revealed to him that, with great effort, Gaster was able to have a hard, tangible body, as opposed to the viscous magic that he was generally able to pull together. And Grillby was finding it hard to concentrate on much else.

 

For the longest time he had found himself with a fleeting thought here and there, usually about touching Gaster. He wanted to know what it felt like. He wanted to know that he could, in fact, touch the man without harming him. He had no trouble touching others, but he wasn’t certain that the other man’s molecular structure would be compatible enough with Grillby’s to not catch on fire. He wasn’t sure if determination was flammable.

 

And now that he knew about Gaster’s solidifying abilities, he was more curious than ever.

 

Thinking about it was starting to cause Grillby’s entire being to throb. With a groan he leaned his elbows on the bar counter, setting the cup down an arm’s length away before he held his face in his hands. An image began to form in his mind behind closed eyes—an image of Gaster materializing beside him, of Gaster chuckling and ducking beneath Grillby’s arms, of his face suddenly being far too close.

 

Gillby felt a shiver go through his flames. In his mind, Gaster’s hand caressed his face as his lips pressed to Grillby’s neck. He chuckled out loud softly—of course Gaster could touch him in his mind. This would have to do for now. Grillby reached up and gripped the back of Gaster’s skull.

 

Gaster grinned against Grillby’s fiery form and began to kiss all around Grillby’s collar. Grillby’s flames crackled, a sound that filled the room, alongside Grillby’s sighs. One of Gaster’s hands ran through the flames atop Grillby’s head while a second tugged his shirt from the waistband of his pants. The cool fingers danced beneath the fabric of Grillby’s shirt and vest, crawling from his side to his back along his waist and then up, to flatten in the middle of his back. A…third hand tugged at Grillby’s waistband.

 

Grillby shivered again, enraptured by his visions, and tilted his head back to allow more room for Gaster’s kisses. The man’s teasing hands were touching all over beneath his shirt and vest, both of which were by now entirely unbuttoned and being pulled down his arms by two of Gaster’s hands. Grillby let out a soft moan, his eyes fluttering open.

 

What he didn’t expect was to see Gaster’s ghostly white face, dusted with a blush of indiscernible color, smiling just inches away. Grillby’s flames flared out in astonishment for a moment before two of Gaster’s hands pulled his face against his. A mischievous chuckle echoed off the corners of the walls of the tavern. Grillby wasn’t sure when Gaster showed up, when the images in his head melded with the reality in front of him, but his kiss was stealing the smoke from Grillby’s lungs, and boy was he getting weak in the knees.

 

He also had no idea when he had backed up so close to the shelving unit behind the bar, yet there he stood, his back pressed against the wood (which, he could not burn. He knew, he had experimented). As Grillby kissed Gaster back the goopy man’s hands, reduced now to two, slid down Grillby’s firey arms and laced his fingers with Grillby’s. Gaster’s voice echoed once again around the room, humming a classical tune in a low register while their lips moved against each other.

 

After about two minutes of kissing and humming and swaying, Gaster pulled back and sighed. Grillby opened his eyes to see Gaster shudder a bit and the bits of his form drifting upwards from his body acted as if they were blown away from his body. He was surprised to see goop giving way to opaque, ghostly white neck and shoulders and a lavender flush beneath Gaster’s closed eyes.

 

Grillby watched in wonder and amazement as, ever so slowly, the solid form he had been told about began to appear. When about half of Gaster’s chest was exposed the man opened his eyes, just a bit, just enough to be compelling, and slid back from Grillby about the length of a step. One of his hands, the only one still laced with Grillby’s, pulled the flame’s arm gently as it followed its owner. For a moment, Gaster glitched and his main form disappeared, only to reappear a few feet away, right near the bar counter.

 

Grillby stepped towards the other man, guided by the hand that held him gently by the fingers. His flames crackled in anticipation and the thrum of his soul became hard in his chest. Gaster grinned and released Grillby’s hand, reaching back to lift himself onto the counter.

 

Grillby smiled to himself—he couldn’t help it, it was far too cute to see the man’s dripping and slender form hunched up on his bar counter and the dark pool of viscous magic forming on his floor. Legs became discernable, though from around his midriff down it was still dark and glimmering with a thick coat of goop. It was even cuter when Gaster’s knees turned in towards each other and the look on his face became embarrassed.

 

Grillby walked forward and moved Gaster’s knees apart just enough that he could fit his form between them, and rested his hands on the bar counter on either side of the other man. Gaster was seated far enough back that his knees were the only bits of him currently in contact with his love—a position he hoped to change momentarily. The thin man bit his lip gently, admiring the flames of Grillby’s arm as they licked up through the hole in Gaster’s right hand.

 

Grillby felt his core heat up and he couldn’t help himself. He tilted Gaster’s face up for their eyes to meet, and then he kissed him again, hoping Gaster found it as intense as he tried to make it. He had no idea, but he suspected he might, as Gaster gripped his arm tighter and a small, deep growl came from the throat that Gaster now possessed.

 

It had never occurred to Grillby before, but Gaster’s voice never seemed to really come from him directly until now. As he continued to kiss his love he reached up a hand, pressing his fingers gently to Gaster’s throat. The vibrations of Gaster’s deep moans shivered through Grillby’s arm and struck him right in the core. He gasped a little at the sensation, then groaned softly, slipping his fiery tongue into Gaster’s mouth.

 

 Gaster’s lips closed gently around the thick of Grillby’s tongue. Grillby could feel the other man sucking on it and his own rough tongue rubbing against it, even curling around it. This was something the flame monster had never considered before, but now that it was happening, he wondered how he would fare in his spare time without it.

 

After a few moments of this, the wet sounds of mouths and the intense crackling of Grillby’s flames, Gaster released the appendage with a gasp of air which was released with the faintest whisper of the words, “touch me”.

 

Grillby shivered again. This was far better than what he had been imagining when all of this began. And he was quick to comply with Gaster’s request. Surprisingly, the area where Grillby expected hip bones and genitals was still covered in goop.

 

Gaster spoke without prompt. “I-I wasn’t sure,” he said softly, “what you would prefer, so…”

 

Grillby, honestly, wasn’t sure either. He just wanted Gaster, about that much he was completely certain. His fingers dipped into the goop between Gaster’s legs.

 

And Gaster gave a high pitched, somewhat strangled cry. Grillby tensed and tried to withdraw, but Gaster was much quicker. His head fell forward and his hand gripped Grillby’s wrist, holding it where it was.

 

“Gaster?” Grillby questioned softly, his flames crackling with concern. “Did I hurt you? Does it burn?”

 

Gaster shook his head almost violently, his hips stuttering forward against Grillby’s fingers. This, of course, made him grit out a strangled groan. It was pretty easy to tell that whatever the man was feeling, it was good, and so Grillby probed forward a bit more, testing how far he could go in the goop. It was odd, there seemed to be an opening within the substance, one that was twitching, and seeing as there was no certainty that it could be analogous to any genitalia that Grillby was familiar with, he just sort of went with it. When the tips of his fingers made contact with the taut area around the opening, Gaster groaned again, deep and rumbling. The tips of his fingers dug into Grillby’s arm.

 

The man of fire chuckled to himself and pressed a kiss to the top of Gaster’s head, still resting on his shoulder, as he began to stroke around the area he had found, every now and then dipping the tip of a finger into the opening. Suffice to say, Gaster quickly became a wreck. His knees squeezed against Grillby’s sides and a black liquid that could be called drool began to leak from between Gaster’s lips. It wasn’t long before Grillby was inserting two fingers deep into the hole, which seemed to be throbbing, and pulling them back out slowly, over and over, in long strokes.

 

The noises Gaster made were mostly whines and groans that were drawn out with the work of Grillby’s hand. The goopy monster was somewhat regretting his choice to pull together this solid form, because the energy and concentration it took disallowed him from spawning more than one or two hands (at this moment only one), at least for now. Which was a shame, because he wanted to touch Grillby everywhere, and could only manage to keep a vice grip on the man’s forearm.

 

It was on the heels of this thought that the fingers were gently withdrawn from Gaster’s crotch area. Grillby’s hand patted the hand on his arm twice, which got Gaster’s attention enough for him to look up at his lover again. Of course, the look didn’t last long, because as he removed his hand from Grillby’s arm he noticed said arm moving back, and the hand at the end of it, which was dripping goop swathed in fire. These drops dissipated as they detached from the source, but it still looked hot as hell for Gaster’s literal essence to be on the fingers of the softspoken barkeep.

 

Those fingers then began to remove said barkeep’s pants.

 

A chill went up Gaster’s back, beginning from the base of his spine. Following said chill was a wave of heat; he knew his face must be purple, but he couldn’t keep his eyes off of what his lover was doing, and the beautiful fire dick that made its appearance rather quickly. The core of it was deep indigo, much like Grillby’s entire torso at this point, and Gaster was not only intrigued, he was greedy, immediately wanting all of that as deep inside of him as possible.

 

The two men kissed again, deeply, as Grillby lined himself up with where his fingers had been. Gaster’s hand wrapped around Grillby’s dick gently, stroking it a small bit as he helped to guide it. Both men let out long, drawn-out moans of bliss against each other’s mouths when Grillby finally sank himself inside the other, but both were too far gone to care, and Grillby did not stay still for very long. Before he was even fully within his lover he pulled back, only to immediately thrust back in. As he worked up a rhythm, Gaster once again began to suck on Grillby’s tongue, and even curl it around large, sharp teeth that Grillby apparently hid behind his magma mouth. His hand came up and removed Grillby’s glasses, which, admittedly, he should have done earlier, but better late than never.

 

Neither Grillby nor Gaster lasted very long once Grillby was going full force inside of Gaster.  The loud sounds of flames crackling filled the tavern, along with slick sounds of Gaster’s material, and of course the breathy, loud, grunting moans that came from the throats of both men. And then, the heat and the pressure and the pleasure built up, as they should, and Gaster came with a high pitched wail, tossing his head back, his fingertips digging into the back of Grillby’s neck. Grillby’s head was bowed, bent over to nip at Gaster’s shoulder, and he came as well, before Gaster’s orgasm was over with.

 

Grillby’s fire flared brightly and he rested all of his weight on his hands, which were pressed to the bar counter, as he huffed, trying to catch his breath. Meanwhile, Gaster lost all control of his form and his concentration, and his solid form collapsed into a puddle. This should have surprised or unnerved Grillby, but when he opened his eyes to see an embarrassed expression on a pale face looking up at him from the floor between his feet, he could only chuckle.

 

“Oh, Gaster,” Grillby laughed, shakily bending and sitting on his knees beyond the majority of the puddle. No doubt the man was mortified. To have such an amazing experience, and then to collapse once again into amorphous magic? How bizarre indeed, not to mention a mood killer.

 

Gaster’s eyes shifted between Grillby’s knees, upon which both hands rested palm up, as if inviting him in for a hug. In fact, the man didn’t even look upset, just tired, flushed from great sex, and maybe a bit amused. Of course, Gaster thought, he was being silly, and he rose a bit, just enough that when he moved forward his head rested on his lover’s chest and the rest of him draped over his legs.

 

Grillby held Gaster’s body as best he could. The two began to chatter back and forth, complimenting each other, kissing every now and then, discussing how Gaster had managed to show up in Grillby’s tavern without him noticing.

 

The next day, they knew, nobody would ask any questions. Nobody would see hickeys on skin made of fire, nobody would see stains from magical goo that dissipated quickly, and nobody would see Gaster. Knowing this made Grillby a little sad, and when he expressed this, it seemed that Gaster felt the same. But it really didn’t matter, did it?

 

Gaster slid Grillby’s glasses back on his face, smiling at his own reflection in the lenses, and the two chatted softly long into the night.

**Author's Note:**

> talk to me about grillster on tumblr. always taking angst prompts n stuff


End file.
